The present invention relates to an in-house paging system capable of issuing a call request to a pager terminal through an in-house switching unit.
Recently, the in-house paging system has been widely used in hotels, office buildings, etc. With this in-house paging system, units and devices are connected through signal lines and power source lines. When an abnormal condition such as defective disconnection arises in these signal lines or power source lines, it must be notified immediately to a maintenance staff, etc. and monitored by a reasonably priced abnormal condition monitor.
FIG. 1 is a block diagram for indicating an in-house paging system of the prior art technology. In FIG. 1, 1 is an in-house switching unit (PBX) for accommodating a plurality of extension terminals 2-1 and 2-2.
4 is a call controller connected to the in-house switching unit 1 for interfacing in response to a call request from the extension terminals 2. It comprises a plurality of a call control interface units 401, a controller 402 having its own memory 403, and a modem 404.
The call control interface units 401 are provided between the in-house switching unit 1 and the controller 402 and control the transmission of data, etc. between them. Each call control interface unit 401 comprises a PBX interface unit 4011, a voice generator 4012 for generating a voice message to the extension terminals 2, and a DTMF detector 4013 for detecting a DTMF signal issued by the extension terminals 2 from a dial or pushbutton phone unit.
The controller 402 comprises a microprocessor unit (MPU) for sending a necessary control signal to each of the call control interface unit 401 and the modem 404.
The modem 404 modulates/demodulates a signal to and from a transmitting unit 5 if necessary.
5 indicates a plurality of transmitting units connected to the call controller 4 and distributed to a number of points. One transmitting unit 5 comprises a modem 501, an encoder 502, a decoder 503, a sending or transmitting unit 504, a receiving unit 505, a controller 506, a switch 507, and an antenna 508.
The modem 501 modulates/demodulates a signal to and from the call controller 4, if necessary. The encoder 502 encodes a signal from the modem 501. The decoder 503 decodes a signal and then sends it to the modem 501. The sending unit 504 pre-processes for transmission a signal from the encoder 502 then transmits it through the switch 507 and the antenna 508. The receiver 505 pre-processes for transmission a signal received through the antenna 508. The controller 506 controls the switching operation of switches, etc. The switch 507 receives a signal from the controller 506 and switches it to the sending or the receiving units.
A pager terminal 6 receives a call signal from the transmitting unit 5 through a wireless transmission line and notifies the maintenance staff of it. A plurality of pager terminals 6 can be provided within the area of one transmitting unit 5.
In the above described configuration, a call request from an extension terminal (phone unit) 2 to the pager terminal 6 is transmitted by the in-house switching unit 1 to the controller 402 after the requesting terminal is identified through the PBX interface 4011.
The controller 402 compares the transmitted number with the contents of the memory 403 to determine whether or not the number is in active service. If yes, it controls the voice generator 4012 to make an announcement such as "Enter a message," then enters the wait state for the input of DTMF.
If not in active service, the controller 402 controls the voice generator 4012 to make an announcement such as "Not in active service", and controls the PBX interface 4011 to disconnect the line to the in-house switching unit 1 after the announcement.
On receiving a DTMF signal, the DTMF detector 4013 detects the number of the depressed button, and outputs the result to the controller 402. If the transmitted signal indicates "a standard statement code 11", for example, the controller 402 controls the voice generator 4012 to issue an announcement such as "A standard statement code 11 will be sent, please hang up and wait." The PBX interface 4011 is then instructed to disconnect the line after the announcement.
On receiving a call number and call data, the controller 402 sends the data to each of transmitting units 5 through the modem 404.
The transmitting unit 5 comprises modem 501, encoder 502, decoder 503, sending unit 504, receiving unit 505, controller 506, switch 507, and antenna 508 as described above.
A signal applied to the transmitting unit 5 through the modem 404 is demodulated by the modem 501 to call data including a call number, etc. Then, it is coded by the encoder 502 into the format of a POCSAG (British Post Office Code Standardization Advisory Group) signal, and transmitted from an antenna through the sending unit 504 and the switch 507.
In this process, the controller 506 of the transmitting unit 5 controls the switch 507 to connect the receiving unit 505 and the antenna 508, then determines whether or not other transmitting units 5 are transmitting data while turning them temporarily in the receiving state. If not, the controller 506 controls the switch 507 to connect the sending unit 504 and the antenna 508.
Next, a monitoring function for monitoring whether or not an abnormal condition such as a defective disconnection arises in signal lines and power source lines is described.
FIG. 1 shows a basic configuration for transmitting data by the in-house paging system. However, a power source and various detecting circuits are provided to operate a transmitting unit other than to transmit data. FIG. 2 shows a detailed configuration of an in-house paging system of the prior art technology.
As shown in FIG. 2, the call controller 4 and the transmitting unit 5 are connected through a signal line 7 and a power source line 8. The signal line 7 transmits a signal between the modem 404 of the call controller 4 and the modem 501 of the transmitting unit 5. An abnormal condition can be detected by the carrier detector 407 and the synchronous detector 408 of the call controller 4, and a carrier detector 512 and a synchronous detector 513 of the transmitting unit 5.
The power source 8 sends electric power from the power source 405 of the call controller 4 to the receiving unit 509 of the transmitting unit 5. The electric power is received by an electric power receiver 509, monitored for voltage by a voltage monitor 510, and applied to various parts of the transmitting unit through a DC/DC converter 511. The call controller 4 is also provided with a voltage monitor 406.
In the above described configuration, the in-house paging system of the prior art technology shown in FIG. 2 monitors for abnormal conditions of the the signal line 7 and the power source line 8 between the call controller 4 and the transmitting unit 5 as follows:
The transmission of a signal between the call controller 4 and the transmitting unit 5 is performed by the modems 404 and 501; the call controller 4 and transmitting unit 5 both perform carrier and synchronous detection; and the call controller 4 manages the monitor information collectively. The voltage of the power source is also monitored by the call controller 4 and the transmitting unit 5, and a monitoring staff monitors an abnormal condition only through the call controller 4.
In the in-house paging system of the prior art technology shown in FIGS. 1 and 2, when a signal line or a power source line enters the disconnection state between a call controller and a transmitting unit, the disconnection state cannot be notified to a maintenance staff because he or she is not supposed to stay at the fixed position and are often away from the call controller. That is, in the prior art technology, a maintenance staff must stand by the call controller to monitor an alarm lamp without staying away from his or her position. Therefore, such a monitoring sytem is inefficient and costly.